[02] WHAT ARE UNIX FILE PERMISSIONS AND HOW DO THEY WORK?
  
   UNIX treats directories, paging, memory, hardware devices, nearly
   everything as a FILE.  Files have modes, and here they are explained.
   NOTE, this is just basic information and not complete.  The following
   should be all you need to know about UNIX FILES.

     u  g  o    l owner    group       bytes    date        file  
   ---------------------------------------------------------------
   drwxr-xr-x   7 nova     users        352 Jul 11 1992 /udd/nova
 
   UNIX treats everything (devices, directories, et cetera) as a file.

   u = user
   g = group
   o = other (everyone else)
   l = links
   d = directory
   t = sticky bit
   p = pipe
   owner = the user id who owns the file
   group = the group that owns the file

   You can use the chown, chmod and chgrp commands to modify files
   chmod (change mode) allows you to alter the permissions of a file
   using "u,g,o" .. for instance:  chmod ou-rx /udd/nova  would make
   the above file unreadable to other users and users in the "users"
   group.  chmod ou+rwx /udd/nova would give all other users access
   to your directory (read and write).
